Because of the power demands at first base, it's rare to see players who are in their early-20s already prospering at the position. First base is frequently reserved for good hitters who don't have enough speed to play elsewhere on the diamond. Prince Fielder fits that mold perfectly. He'd likely be a disaster in the outfield but his bat has a chance to be legendary.
Notes: The level that appears following each player's name is the highest level where the player has registered over 100 plate appearances. We used an age cutoff of April 1st, 2008.
1. Prince Fielder, MIL (5/9/84) - MLB
The youngest player ever to hit 50 home runs in a single season, Fielder led the National League in isolated power last year (.330). His below-average speed limits his ability to hit for a high average (.280 over 1,201 pro at-bats), but other than that, there aren't many holes in the 5-foot-11, 270-pounder's game. He walks a lot (15.8% in 2007), doesn't strike out too much (17.3%), and hits a good amount of line drives (20%). Only Carlos Pena and Alex Rodriguez put up better isolated power numbers than Fielder last season (.345 and .332, respectively). Though it's possible that his body may not endure the rigors of baseball as well as some of his peers, Fielder could reign as baseball's power king for the next 5+ years.
2. Billy Butler, KC (4/18/86) - MLB
I saw Butler play for the first time earlier this spring, and his abilities at the plate really impressed me. He appeared balanced every pitch (ball/strike, taking/swinging), worked the count well, and made good contact every at-bat. I kind of felt like I was watching a righthanded Todd Helton -- the way he controlled each at-bat. The 6-foot-1, 240-pounder only managed a .192 isolated power (21 HR) between Triple-A and the big leagues last season (.291/.374/.483 vital line), so he may not be a 30-home run threat for another few seasons. But the former first round draft pick (14th, 2004) still figures to be an above-average hitter in his prime -- note that DH will likely be his long-term position.
3. James Loney, LAD (5/7/84) - MLB
After struggling to produce in Triple-A last April and May, Loney caught fire and earned a starting job in the big leagues in June. He ended the season as strong as ever -- nine home runs in September. The lefty finished his first extended stay in the big leagues with a stellar .332/.381/.539 vital line (378 plate appearances). We'll be surprised if he's able to replicate that line in his first full season -- Loney's a career .296/.362/.430 minor leaguer -- though he really began to blossom once he reached Triple-A (2006). The 6-foot-3, 220-pounder could be on the fast track toward becoming an above-average big leaguer.
4. Daric Barton, OAK (8/16/85) - AAA
Barton has already registered 782 Triple-A plate appearances and he'll play most of the 2008 season as a 22-year-old. What's more, he missed more than half of the 2006 season due to a broken elbow -- injured it in a collision in Triple-A. So what's the point of rehashing the 6-foot, 225-pounder's Triple-A service time? To demonstrate how advanced and polished he is. Barton is an excellent contact hitter (11.5% K in Triple-A last season) who draws a lot of walks (13.0%). Power has been one of the biggest voids in his game over the course of his minor league career, but he was exceptional in that regard last September in the big leagues. Similar to Loney, Barton's going to have trouble replicating his 2007 big league success (.347/.429/.639 in 84 plate appearances). But if he comes close to matching those totals, he'll quickly become one of the game's elite hitters.
5. Chris Marrero, WAS (7/2/88) - A+
Already equipped with home-run power to all fields, Marrero's a guy who could knock 30+ balls out of the yard a season someday. His power has been pretty streaky to date, but once he's locked in he's dangerous. One of Marrero's main struggles has been making consistent contact (18.9% K last season). Just keep in mind that he made his High-A debut as an 18-year-old and he's on a pace that could put him in the bigs before he turns 22. The 6-foot-3, 210-pounder was an exceptional amateur (15th pick in 2006) and he has shown flashes of immense potential as a pro.
6. Joey Votto, CIN (9/10/83) - MLB
Votto has been an above-average hitter everywhere he's played since the start of 2006. Though May was his only sensational month in the minors last season (.468 wOBA), he had a stellar September with the Reds (.374 wOBA in 90 plate appearances). The career .289/.385/.476 minor leaguer is an exceptional contact hitter with decent speed and power -- also draws a good amount of walks. Votto's likely ready to be close to a league-average regular. And so long as he's playing his home games with the Reds, he'll get a pleasant power boost. The 6-foot-3, 220-pounder doesn't have as much upside as the players above him, but he's still an elite prospect.
7. Angel Villalona, SF (8/13/1990) - R
Any prospect who signs for over $2.0 M is going to play with a big target on his back in the minors. That didn't phase Villalona. The 6-foot-3, 220-pounder hit .285/.344/.450 with a 35.0% extra-base hit rate in rookie ball -- XBH/H. I caught a glimpse of Villalona this spring at Giants' minor league camp. He launched balls over the left and center-field fences and showed soft hands at first base -- he played third last season. Simply put, Villalona has about as much potential as any hitter in the minors right now. His stock could soar as he competes in his first full season in 2008.
8. Justin Smoak, SC (12/5/86) - NCAA
Some people think Smoak is every bit as talented of a hitter as Pedro Alvarez, who could be the No. 1 overall pick in the 2008 Draft. The 6-foot-4, 215-pounder is known for his power bat and good athleticism. He's a sound bet to be a top five overall pick this June. The switch hitter was batting .351/.490/.636 through his first 20 games with South Carolina this season -- note that he plays in a home park that has favored pitchers recently. Baseball Prospectus' Bryan Smith went out on a limb and wrote that Smoak has a chance to be a Gold Glover who delivers 40 home runs a season.
9. Beau Mills, CLE (8/15/86) - A
Mills transferred to Lewis-Clark State (NAIA) after being ruled academically ineligible for the end of his sophomore season at Fresno State. Though it's hard to make much quantitative sense of his NAIA season, Mills impressed the Indians enough to earn their approval as 13th overall pick of the 2007 Draft. A 6-foot-3, 220-pounder, Mills has plus power and a level swing that should allow him to be a solid contact hitter -- Source: MiLB.com. The reason he's below Smoak on this list is because he had a lackluster pro debut (.259/.329/.410 in 281 plate appearances). We like that Mills' isolated power increased at each of his three minor league stops (SS, Low-A, High-A), while his strikeout rate decreased. He has a chance to develop into an above-average regular.
10. Lars Anderson, BOS (9/25/87) - A
Given first round supplemental money to sign after being selected in the 18th round of the 2006 Draft, Anderson had an impressive pro debut (.293/.393/.446) between Low-A and High-A. The 6-foot-4, 215-pounder drew a lot of walks (14.1%) but struck out a lot, too (21.0%). His power numbers could be through the roof this season in Lancaster -- just a .154 IsoP last season. And there's a chance that Anderson will be promoted to Double-A by year's end. He has more questions to answer than the players above him here, but Anderson could firmly plant himself as an elite prospect among the game's elite prospects with a good year.
11. Yonder Alonso, MIA (4/8/87) - NCAA
Born in Cuba, Alonso excelled in the Cape Cod League last summer and is off to an eye-popping .413/.558/.762 start this season. With his powerful bat and advanced strike-zone judgment, Alonso will likely be a top 10 overall pick in the 2008 Draft. This year's college class looks as though it will offer up a better elite core of hitters than the 2006 and 2007 groups before it. So even if Alonso isn't one of the first three college hitters taken this June don't overlook him.
12. Brett Wallace, ASU (8/26/86) - NCAA
Yes, he plays in a hitter-friendly environment, but Wallace's .420/.532/.807 line so far this season is still jaw-dropping. The 6-foot-1, 245-pounder was going to have to hit a ton to justify being a top 10 overall pick this June and so far he's doing it. It's rare for college first basemen to go high in the draft. But Smoak, Alonso, and Wallace may be too good at the plate to slip out of the top half of the first round. Note that though Wallace is playing third base for the Sun Devils this season first base or DH figure to be his home in pro ball -- he played first base as a sophomore.
13. Steve Pearce, PIT (4/13/83) - AAA
After being an above-average High-A player (.358 wOBA) in 2006 as a 23-year-old, Pearce was amazing in 2007. The 5-foot-11, 200-pounder hit .328/.388/.595 between High-A (85 plate appearances), Double-A (335), Triple-A (131), and the big leagues (73). Powerful enough to fit in at first base offensively and athletic enough to be decent in the outfield, Pearce should be able to find at least a few hundred at-bats in the bigs this season. His walk and power rates decreased measurably from High-A and Double-A to Triple-A and the big leagues. We still want to see more out of Pearce before we label him as a potential average regular or more. But he could very well prove worthy of such a title this season.
14. Eric Hosmer, AH (10/24/89) - HS
Yet another 2008 Draft prospect who could prove himself as a top 10 overall pick despite the fact that he appears limited to first base, Hosmer may be the top high school hitter in his draft class -- Source: MiLB.com. According to the article linked above, the 6-foot-4, 210-pounder has "a ton of upside with the bat, both in terms of hitting for average and power and he's surprisingly nimble defensively."
15. Kendry Morales, LAA (6/20/83) - MLB
It wasn't that long ago that Morales was given $3.0 M to sign with the Angels (December of 2004). More than three years later, Morales is still trying to earn regular playing time in the big leagues. The 6-foot-1, 225-pounder has a .256/.308/.411 vital line through 316 MLB at-bats (.324/.368/.516 in the minors). A switch hitter, Morales could eventually become an average big leaguer. His potential rise will be dependent on his ability to hit for power and work the count.
Honorable Mention: Kyle Blanks (SD).
Adam Foster can be reached at adamf@projectprospect.com.